The present embodiments relate to a cylindrical gradient coil arrangement for a magnetic resonance device.
Gradient coil arrangements, such as those used in magnetic resonance devices, are known in the prior art. Gradient coil arrangements additionally provide the basic magnetic field with generally linear gradient fields, which restrict excitation to certain slices or as readout gradients. At least in the homogeneity volume of the magnetic resonance device, the gradient coils of the gradient coil arrangement are able to generate the desired fields as precisely as possible. Complex optimization methods are known for designing the current paths and, consequently, the conductive structures, such that the desired fields may be generated considering as many effects as possible.
Therefore, known gradient coils include numerous conductive individual layers that implement the required current density distributions via complex current paths. The different individual layers may be separated from each other by insulation materials and cooling levels. The individual layers of the gradient coils are joined in a gradient coil arrangement and are joined with a casting material (e.g., epoxy resin) to form a composite structure. However, the usually low thermal conductivity of the casting compound limits the efficiency of the heat dissipation.
In addition, the high current intensities used (e.g., up to 1 kA) and the high magnetic fields (e.g., up to 12 T) provided during the operation of the gradient coil arrangement, which may include gradient coils for the x-, y- and z-axes of the magnetic resonance device, result in high Lorentz forces and, consequently, in severe mechanical stress on the carrier apparatus and the conductive structures. Modal vibrations form in the gradient coil arrangement. Due to the large radiating surface of the coil cylinder formed with conventional gradient coil arrangements, the modal vibrations are converted into audible airborne noise.
Known gradient coil arrangements are also problematic because of the complex disposal methods in which the different materials therein are to be mechanically and thermally separated.
In order to achieve adequate cooling, different water cooling levels with a highest possible throughput of cooling medium are used. Also used are materials with the most favorable heat transfer properties and, simultaneously, adequate electric insulation (e.g., epoxy resin). To minimize the sound transmission to the patient, insulating measures have been proposed, such as, for example, melamine foam. The recycling of gradient coil arrangements takes place, for example, by mechanical comminution (e.g., shredding), and by subsequently removing the conductive metals by melting. Complete recycling (e.g., complete separation) is not provided.